Improvement in platform weighing-scales



- BEST AvAxLABLE com T. PAIRBANKS.

Platform WQghng-Soale.g No. 205,623. Patented July 2,1873.;

N. PETRS. PMOTo-UTHDGNAPHER, wA's'wNGYON. D C.

BEST AvAsLAeLE con' UNITED STATES PATENT Onro- THADDEUS FAIRBANKS, OF

sr. Jonnsnnnv, VERMONT.

IMPROVEMENT IN PLATFORM WEIGHlNG-SCALES.

Specification forming part'of Letters Fntcnt No. 205,623, dated July 2,1878; application filed May 18, 1878.

To all whom it may concern:

Be it known that I, THADDEUS Fhinnawks, of St. J ohnshury, Caledoniacounty, in the State of Vermont, have invented certain new and usefulImprovements relating to Platform- Scales, of which t-he following is aspecification:

The invention is intended more particularly for what are known asdrop-lever scales but it may be used with advantage without thedrop-lever mechanism.

The object is to make the working more free. It allows vibrations andavoids cramping and friction on the knife-edges more completely andperfectly than any ordinary construction. It allows the platform to beremoved and replaced with facility.

The following is adescription of what I consider the best means ofcarrying out the invention.

The accompanying drawings form a part of this specification.

Figure 1 is an end elevation of the entire scale, partlyin section.Fig.2isaerosssection through the lower part, the. upper parts beingpartly shown. The remaining' figures show a modification of a portion.Fig. 3 is a side view, and Fig. 4 a plan view, of a slight modiiicationof parts.

Similarletters of reference indicate like parts in all the 1i gures.

A is an ordinary foundation-casting, having an upright port, A, with ahorizontal arm, A2, rigidly connected, and supporting a dropleverattachment, B, turning on a pivot, l), and securedby a catch, b', sothat it may hold up the weighing-beam D by the connection C, and lowerit with the weigh-rod E and its attaclr ments, all in the ordinarymanner.

The novelty lies in the work under the platform. The platform may be asingle casting of cast-iron, the main bod yof which is indicated by G,and the bearing-arms, extending downward therefrom, by Gpl, the shorterlugs, which check the endwise motion, bei n g represented by G2. Thelower ends of the bearing-arms G1 are formed with V-shaped cavities, asrepresented by g', which receive a longitudinal bar, H, which latter areeach formed with a corresponding V-shaped ridge, h.

The long lever I and short lever J may be of the ordinary long-approvedconstruction, as indicated; but the object placed on the platform actsby gravity on the knife-edges of the levers, not directly, but throughthe medium of the bars H and of pendent links K, which may be eithersimple or compound, and which are free to oscillate on the knife-edges jof the respective levers I J at their upper ends, and which so engagewith the bar H that the latter may swing. The forms of these links K andtheir mode of engagement with t-he bars I-I may vary. It is notessential to correct weighing that the engagement of these links K withthe bars H be frictionless, nor that it be confined to any particularposition. In other words, the engagement of the links K with the bars Hmay be by knife-edges, or by a simple rolling contact, like the links ofa chain. No difference will bemadein the weighing by any possible amountof friction at the joints. A great friction at the connections of thelinks K with the bars H will simply retard the freedom of the swingingof the platform. It will have no effect on the leverage, and noappreciable e'ect on the freedom of working of the levers I J.

One construction of the links K is sliownin Figs. 1 and 2, where thelink is compounded of two parts, linked together.

Another mode of construction is by a simple link, as shown in Figs. 3and 4. These figures show the knife-edges It set in the forked ends ofeach har H. I esteem this the preferable construction, but theconstruction shown in Fi 1 and 2, or various others, may be adopted.

The ordinary raising and lowering of the plat-form by the tilting of theweighing-beam Din the act of weighing is allowed by the slight turningof the levers I J, the links K and the bars H maintaining theirpositions, except to rise and sink to correspond with the platform. Inthis movement of the levers I J the knife-edges j describe so large anare that the links K swing to an appreciable extent, thus inducing aturning motion at the junctions ofthe parts H and K; but a slightfriction under these conditions is not objectionable. The knifeedgeconstruction shown in Figs. 1 and 2, by presenting no friction, will205,623 BEST Amr/lere coa-v ne drop-lever motion easier; but a conablefriction atthosc j unetions involves no preciable mischief.

When, by the operating of the drop-lever B, the levers I J and theconnected bars H are lowered out of engagement with the arms G,

the latter remain idle, and are liable, by any sufficient force appliedto the platform, to change their positions horizontally to a smallextent, so that when the bars H are again lifted they will not come`into contact in the same positions as they parted. Again, the bars Hareliable to swing or move, by some chance, one way or the other, sothat the points of engagement may not be the same; butthe V- shaped toph of each bar H and the V-shaped recesses g in each arm GrI cause themto slide upon each other in coming in contact, and insure that theultimate bearing position shall be practically the same.

No harm can result from a slight chan ge of position of these parts. Theweight will be always transmitted through the links K to the knife-edgesi j in an absolutely vertical line.

Changes in the bearing of the arms Grl gupon the bars H h' can onlychange the position in which the platfonrn G is supported. Such changes,when thus constructed, are in theory, as in practice, unworthy offurther mention.

I claim as my inventionl. The longitudinal bars H 7L andsuspending-links K, in combination with a platform, G, having notchedarms G resting on said bars, levers I J, and suitable connections to aweighing-beam, D, as and for the purposes herein specified.

2. The longitudinal bars H It and suspending-links K, in combinationwith a platform, G, having notched arms G, levers I J, havingknife-edges t' j, weigh-rod E, and beam D,

substantially as herein specified.

In testimony whereof I have hereunto set my name in presence of twosubscribing witnesses.

THADDEUS FAIRBANKS. Witnesses:

E. D. BLODGETT, D. DEAN PATTERSON.

